The prior art is replete with different techniques and processes for fabricating semiconductor devices such as metal oxide semiconductor (MOS) integrated circuits. In accordance with typical fabrication techniques, a MOS integrated circuit is formed by creating a device structure on a semiconductor substrate, where the device structure includes a gate stack formed on a layer of semiconductor material, and source and drain regions formed in the semiconductor material to define a channel region under the gate stack. Some integrated circuit devices are fabricated using a replacement gate technique; in accordance with this technique, temporary gate material (typically polycrystalline or amorphous silicon) is removed, temporarily forming a trench-like structure (hereinafter “trench”), and then replaced (filled) with a different gate metal.
Current replacement gate metal fill processes for p-type MOS integrated circuits (PMOS) include the conformal deposition, typically by atomic layer deposition (ALD), of a thin layer of barrier material, such as a titanium nitride material, followed by the deposition, typically by chemical vapor deposition (CVD) of a tungsten or aluminum metal. However, as semiconductors are scaled smaller, for example in the 20 nm generation and smaller, the thin barrier material layer takes up a larger and larger percentage of the volume of the trench, and as such increases the resistivity of the gate beyond desirable levels. For example, in combination with tungsten or aluminum, greater than 50 Å (in thickness) of barrier material (e.g., titanium nitride) is required to achieve a p-type workfunction. 50 Å takes up a significant percentage of the volume of the trench, and therefore creates an undesirably high resistance in the gate structure (known as line resistance). Furthermore, some traditional metals, such as aluminum materials, tend to form voids if the trench is too small, for example in the size of trench that is typically formed in 20 nm and smaller generation devices.
As such, it would be desirable to provide a replacement gate material fill technique that overcomes the above-noted difficulties currently encountered in the art. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings, the brief summary, and this background of the invention.